Rising temperatures will increasingly threaten security, health and food supplies, and exacerbate poverty and damage species and habitats, the report also warned.

‘Man-made’

The world is in “an era of man-made climate change” and has already seen impacts of global warming on every continent and across the oceans.

Vicente Barros, co-chair of the IPCC study on climate change impacts, vulnerabilities and adaptation, from the University of Buenos Aires, Argentina said: “We live in an era of man-made climate change.

“In many cases, we are not prepared for the climate-related risks that we already face. Investments in better preparation can pay dividends both for the present and for the future.”

We live in an era of man-made climate change – IPCC’s Vicente Barros

The world has seen changes in recent decades to water resources as a result of melting glaciers and differences in rainfall, and reductions in wheat and maize yields.

There has been a decrease in the number of people dying from the cold but an increase in heat-related deaths in some areas, such as England and Wales, the report suggested.

Species including fish stocks are shifting their ranges, coral reefs are being damaged and wildfires are becoming more frequent.

‘Increased risk of flooding’

The report on the impacts of climate change said rising temperatures are expected to lead to increased risk of flooding, more droughts and heatwaves, drive species extinct and cause forests to die in many regions of the world.

Food security will be hit by reduced yields in the major crops of wheat, rice and maize, while climate change will also exacerbate existing health problems, and lead to more heat wave-related deaths, malnutrition and disease.

Increasing numbers of people are set to be displaced by extreme weather events, and the impacts of rising temperatures could help increase the risk of violent conflicts by worsening problems such as poverty, the report said.

Recent extremes such as heat waves, droughts, floods and wildfires show how vulnerable humans are to variations in climate, the study warned.

In Europe, there will be increased economic losses and more people affected by flooding in river basins and coasts, in the face of rising sea levels and heavy rainstorms.

Most of the flood damage can be avoided by measures such as flood defences, but the costs of increasing protection will be high.

Professor Sam Fankhauser, of the London School of Economics and a contributing author to the report said: “In the UK and the rest of northern Europe, we will need to cope with increasing risks from coastal and inland flooding, heat waves and droughts.

“The UK and all rich countries must also provide significant support to help poor countries, which are particularly vulnerable, to cope with the impacts of climate change.”

The report from the IPCC forms the second part of a wide-ranging review of the evidence surrounding climate change.

The first part of the “fifth assessment report” which looked at the science of climate change, concluding there was a 95 per cent chance that humans were responsible for the majority of global warming, was published last year.

The second part of the study drew on contributions from hundreds of experts from 70 countries, and more than 1,700 expert and government reviewers.

‘Alarmist’

However, one of the 70 authors of a draft UN report on climate change said he had pulled out of the writing team because it was “alarmist” about the threat.

Dutch professor of economics at Sussex University Richard Tol said he disagreed with some findings of the summary to be issued in Japan on Monday.

“The drafts became too alarmist,” he said.

Professor Tol said the IPCC emphasised the risks of climate change far more than the opportunities to adapt.

He said farmers, for instance, could grow new crops if the climate in their region became hotter, wetter or drier. “They will adapt. Farmers are not stupid,” he said.

He said the report played down possible economic benefits of low levels of warming. Less cold winters may mean fewer deaths among the elderly, and crops may grow better in some regions.

“It is pretty damn obvious that there are positive impacts of climate change, even though we are not always allowed to talk about them,” he said.

But he said temperatures were set to rise to levels this century that would be damaging overall.